There are several types of prior art catheters designed for insertion into a body cavity of a patient. These typically employ an anchoring device in the end of the catheter intended to reduce the risk of accidentally pulling the catheter out of the cavity. One type of such catheter employs a suture that is accessible from outside of the patient, passes through a connector on the catheter into internal opening (or lumen) of the shaft of the catheter. It then exits through the tip and reenters the lumen at a more proximal location where it can be secured inside of the lumen or on the connector. A medical professional inserting the catheter then pulls on the suture causing the distance between where the suture exits the catheter and where it reenters the catheter to be reduced. This effectively causes the distal section of the catheter to form an anchoring shape. The suture is then secured holding the distal end of the catheter in this anchoring shape. If the catheter is pulled, its distal end in the anchoring shape is pulled against the wall of the cavity, resisting the pulling force, thereby preventing the catheter from being pulled out of the patient.
The catheter may also be manufactured with a pre-formed curl at its distal end, to facilitating curling once in the body cavity. To insert this type of catheter, a stiffening rod is placed through the lumen of the catheter causing it to straighten out. The catheter and rod are then inserted into the body cavity. Once inserted, the stiffening rod is removed causing the shaft of the catheter to curl to its original pre-curved shape. The pre-curved shape interacts with the internal surface of the cavity to resist removal of the catheter once inside a body cavity.
Alternatively, a guide wire is inserted using accepted medical procedures into the body cavity. A dilator may be used to open the insertion site before sliding the catheter over the guide wire and into the body cavity.
A suture is used to hold the catheter in its position after the catheter returns to its original pre-formed shape. The suture also provides increased retention capabilities to the catheter.
Since these catheters are inserted into a patient who is typically under local anesthesia, the patient is awake and uncomfortable. The patient may also be moving or fidgeting during the procedure while the physician is trying to secure the suture. The physician also has to secure the suture when wearing protective gloves. In addition, the flow of bodily fluids typically infected and unpleasant may be flowing from the catheter.
If a physician improperly inserts, or improperly operates one of these devices, substantial complications may arise that are described in detail later. These catheters should be designed such that they are intuitive to operate requiring little or no instruction. Such a device would minimize risk of improper insertion, and the time spent in ‘guesswork’ during a procedure in which the physician ‘learns’ the device.
Several devices are currently in use to secure the suture after the catheter has been placed. One prior art design employs a catheter shaft connected to a stopcock at the proximal end. The stopcock has an internal barrel that rotates in a cylindrical housing. The barrel has a center hole passing through it that may be aligned with the lumen of the catheter by rotating the barrel using a key attached to the catheter by a string or suture. A suture passes from the distal end of the catheter, through the shaft of the lumen, through the center hole in the barrel, and out of a proximal end of the stopcock. As the stopcock barrel is rotated the center hole is no longer aligned with the catheter lumen and seals off the lumen. As the barrel rotates, it also pinches the suture between the sidewall of the barrel and the stopcock housing on both sides of the barrel. The pinching of the suture secures it in place.
That design has disadvantages of not being intuitive to operate, not being as comfortable as other designs, compromising the integrity of the suture, requiring a separate key, and not providing a tactile or audible signal that the catheter is in the locked position as discussed in detail below.
The stopcock housing is marked with a lock and unlock position. If in the locked position, a medical professional intending to drain fluids from inside of the patient may mistakenly rotate the barrel from lock to unlock. This action will also release the suture allowing the catheter to be pulled out of the patient. Therefore, it is not very intuitive to operate.
Since this design employs a stopcock and barrel, the size of the connector is larger than most other designs. The larger size coupled with the fact that it does not have a soft covering, causes considerable discomfort to the patient. The catheter may be implanted in awkward locations and remain in place for extended periods of time, causing additional discomfort to the patient.
When the stopcock barrel is turned to secure the suture between the center opening walls in the barrel and the stopcock body, the contact is localized to two small pinch points. These pinch points flatten the suture causing weakened points in the suture. These weakened points are more prone to breakage than undamaged portions of the suture. Once the suture breaks, the distal end of the catheter is no longer locked in place, increasing the risk of catheter dislodgement.
Another problem is that even though there is a visual indication that the catheter is in the locked position, there is no positive tactile or audible feedback, (such as a snap) to the physician indicating when the connector has been placed in the locked position. This is a useful feature that is lacking in this design.
Another prior art catheter device is a c-clip design that employs a hub with a circumferential inset, connected to the proximal end of a catheter. A suture runs from the distal end of the catheter, through the lumen of the catheter, to an exit point through the sidewall of the hub. To lock, the suture is wrapped around the circumferential inset. A c-clip is provided that is intended to fit around the periphery of the hub, and clipped into the inset over the suture, thereby securing the suture.
The c-clip design is difficult to operate, even under optimum conditions. The c-clip is small and difficult to align in the inset. It will not snap into place unless properly aligned.
In addition to being difficult to lock, it is fairly easy to unlock. A patient, without the aid of tools, can pop the c-clip out of the inset, thereby causing the catheter to become unlocked. Therefore, it is not very tamper-resistant.
This design also does not make use of a smooth protective covering, thereby having the additional disadvantage of being uncomfortable to the patient.
There is another design on the market that employs a simple side hole in a catheter hub connected to the proximal end of a catheter. A suture extends from the distal end of the catheter, through the lumen, and passes from the lumen to outside of the hub through the side hole. A conical flexible strain relief portion surrounding the catheter shaft is designed to be pulled up over the hub and side hole, both sealing the hole and securing the suture.
Even though this design is very intuitive to use, employs a soft protective cover to aid in patient comfort, it does not properly secure the suture in place. If a moderate amount of pulling force is exerted on the catheter, the suture will slip causing the catheter to become unanchored, and increase the risk that the catheter will move out of position or become dislodged. The catheter is difficult to lock since tension must be maintained on the suture during the locking procedure to keep it from unraveling.
Even if the suture does not slip on its own, a patient may easily unlock this design by simply pulling the strain relief portion off of the hub. Therefore, this design is not very tamper-resistant.
One additional problem is that, due to the nature of the design, when the strain relief is not placed over the hub, the side hole opening leaks fluids that are in the catheter lumen.
Like the stopcock design above, it provides visual indication that it has been placed in the locked position, however it lacks positive tactile or audible feedback to the physician indicating that it has been placed in the locked position.
U.S. Pat. No. 6,508,789 assigned to Merit Medical Systems, Inc. of South Jordan, Utah ('789 patent) describes another prior art drainage catheter having a pre-formed curl and a suture that pulls on the distal end of the drainage catheter as described above. The '789 patent further describes a 2-part (proximal and distal) hub that interacts with the suture to pull in the suture and lock the suture in place. A plurality of fingers on the proximal hub forces the suture into a corresponding plurality of channels of the distal hub that mate with the fingers. This effectively pulls in, and shortens the suture. A device according to the '789 patent functions to cause the distal end of the catheter to curl toward the proximal end that locks into position.
A drawback with that device is that it is only capable of pulling in a fixed length of suture into the hub, and cannot be adjusted to pull more, or less than this fixed length of suture into the hub, as needed.
A second disadvantage is that the use of the fingers in channels, as opposed to the medical professional manually pulling on the suture, causes a loss of tactile feedback. The medical professional uses tactile feedback to determine if the tip of the catheter is moving freely or if it is trapped, caught or tangled when anchoring the catheter.
A third disadvantage is that since there is no tactile feedback, if the device is trapped, caught or tangled, and the medical professional ‘forces’ the device to lock, the increased friction of the suture as it passes through each of the plurality of fingers and channels may cause breakage of the suture, making the device unusable.
The design in the '789 patent is also not very intuitive to operate. The physician pushes the proximal hub into the distal hub thereby pulling in a length of the suture into the hub. Therefore, it is not very intuitive to ‘push’ to ‘pull’ in the suture.
One additional drawback with that design is that there are a series of internal crevices within the fluid path that cannot be flushed and cleaned. As specified above, these types of catheters are typically used to remove infected bodily fluids. The fluids, if allowed to remain in the hub of the Sinnot design could cause considerable infection.
U.S. Pat. No. 5,399,165 assigned to Cook, Inc. ('165 patent) describes a drainage catheter employing a similar distal curl and suture arrangement. The '165 patent describes the use of a lever on the catheter hub that actuates a cam causing pressure to be placed on the suture, at a specific point, thereby locking the suture in place.
This design results in a large, bulky catheter connector that is uncomfortable for the patient. The design is also not very tamper resistant since the patient, without the use of tools, can flip the lever to unlock the suture, allowing the catheter to become unanchored, causing increased risk that the catheter will move out of position or become dislodged.
This design also suffers from the problem that there is an open hole to the inside of the lumen when it is in the unlocked position (when the lever is up), thereby allowing leakage.
One of the greatest shortcomings of this design is that it employs a single localized point of contact with the suture. Therefore, it does not positively secure the suture, and allows the suture to slip.
Moreover, the localized pressure on the suture where the cam presses against the suture, employed to secure the suture, causes a weakening of the suture at that point. If the suture breaks, there is the possibility that the catheter will reposition itself so that it does not function as well as intended, or potentially can become dislodged. This may require a medical procedure to be performed to insert a replacement catheter.
Therefore, there is a need for a catheter designed to be secured in a body cavity that: a) is simple to operate, b) is intuitive to operate without requiring much instruction, c) is comfortable to the patient, d) is small and not bulky, e) positively secures the suture, f) minimizes damage to the suture, g) provides audible, or tactile feedback when locked, h) is sufficiently tamper-resistant, i) can be completely flushed and cleaned, j) does not leak when in either the locked or unlocked positions, and k) does not loosen when attached to, or detached from other equipment.